In day-to-day use, electromagnetic field (EMF) meters are used to diagnose problems with electrical wiring and power lines and to get readings on working appliances.

On television, professional ghost hunters frequently use EMF meters in their toolkits, but why is this? Let's take a look at what EMF meters measure, survey the different types of meters, and find out how EMF meters became front line instruments for paranormal exploration.

What do EMF meters measure?
EMF meters detect fields emitted by moving electrically charged objects. Electromagnetic field theory lies at the combination of an electric field, produced by a charged object, and the magnetic field created when the charged object moves. Scientists previously separated electric fields from magnetic fields, but a combination of the two fields models reality better.

Electromagnetic fields are created using alternating current and direct current, but with different results. EMF meters measure fields produced by alternating current – the type of electricity surging through your microwaves and television. This current moves back and forth fifty to sixty times a second. Direct current fields are stationary, like the earth's magnetic field, and cannot be measured by most EMF meters (but that's okay, as it would essentially be background signal).

Day-to-day, EMF meters are used for diagnosis of problems with electrical wiring, power lines, and electrical shielding effectiveness, but professional ghost hunters swear by the inclusion of an EMF meter in their toolkits.

Buy your own EMF Meter from anywhere from $1 to $200
EMF meters come in two flavors: single axis and tri-axis. A single axis meter measures the EMF in one direction, and you have to turn the meter in order to acquire proper data about an electromagnetic field. Most EMF meters available for sale are single axis meters, as they are considerably cheaper and offer user friendly bells and whistles like digital readings and LED lights.

I purchased a high-end single axis meter, the Lutron 822-A Fully Digital EMF Meter, and it readings consistently increased when I probed EMF sources, such as my microwave, laptop, and flat screen television. The single axis aspect is a definite problem –- it's difficult to read the digital display when you are turning the meter to manually measure all three axes. Tri-axis meters allow for much more detailed data acquisition, but are considerable more expensive (often selling for $150 or more).

If you are extremely cheap and just want to play around with an EMF meter, several apps are available for download on your iPhone that range from free to a couple of bucks. These apps make use of the magnetometer in your iPhone, the same piece of technology that allows your phone to serve as a compass. These are not the most reliable meters, but they are fun and give an idea about how they work. The ones I tested worked well with high EMF sources, like microwaves, but gave jumpy readings when I walked around the house. Either the readers were inconsistent…or my house is haunted.

Is there correlation between electromagnetic fields & ghosts?
Peter Venkman and Egon Spengler used PKE meters in Ghostbusters, but "real" ghost hunters use EMF meters as a key part of their specter tracking arsenal. Brian Harnois of The Atlantic Paranormal Society (TAPS), explains:

The prime sensory instrument of any ghost investigation is an EMF meter.

Ghost hunters use the meters to look for spikes in the EMF signal, with the spikes suggesting a change in electrical current, and thus a spirit being.

The association between EMF meters and ghosts is frequently made, but there is no firm evidence connecting the two. Researchers show that high electromagnetic field strength often correlates with personal experiences of hauntings, but that is a measurement of the observer and not a ghostly subject.

Professor Johnjoe McFadden from the School of Biomedical and Life Sciences at the University of Surrey proposes that the conscious mind consists of an electromagnetic field, a field that does not disintegrate when we die. The firing of electrical impulses along nerves in the brain is sort of like an alternating current system as well, but with a lot more directions and cascade effects.

You have to personally connect electromagnetic fields to apparitions
Most likely, "ghost hunters" turned to EMF meters as the instruments yield tangible data — data collection lends credibility to an activity that lends itself to the world of pseudoscience.

EMF fields are present in the world around us, and if you subscribe to the assumption that ghosts contain some electrical residue, EMF meters would be a good way to detect their presence. As of now, no evidence connects the use of EMF meters for ghost detection, but if you are running around looking for ghosts, concrete evidence is probably not a necessity.